Manufacture of metal oxids



Patented Sept. 16, 1930' UNITED STATES PATENT OFFICE ROBERT GRIES SBACHAND JULIUS EISELE, OF LUDWIGSHAFEN-ON-THE-RHIHE, GER- MANY, ASSIGNORS TOI. G. FABIBENINDUSTRIE AKTIENGESELLSGHAFT, OF FRANK- FORT-ON-TEE-MAIN,GERMANY, A CORPORATION OF GERMANY No Drawing. Application filed November29, 1926, Serial Ito. 151,594, and in Germany Deigember 11, 1925.

7 When metal oxids, for example those of thorium, aluminium, iron,chromium and the grained gels of greatmechanical strength.

It has been found that such gels can be prepared by dehydratinghydrosols, but satisfactory results are only obtained when starting fromhighly concentrated hydrosols the dehydration of whichrequires only ashort time. However, the preparation of highly concentrated hydrosols israther difficult.

We have now found that highly concentrated hydrosols of'the said metaloxids canbe obtained by peptizing freshly precipitated hydroxids (after.washin until free from electrolyte and preferably a as far as possible,for example by treatment in a filter press) by means of chemical agentssuch as suitable salts or acids while at'the.

same time subjecting them to a mechanical dispersion by treatment forexample in a ball mill or beating cross mill or by vigorously stirringor the like. By this means highly concentrated sols can be obtained withthe aid of very small quantities of peptizing agents, as the latter arepresent in a comparatively high concentration due tothesmall quantity ofwater. A small content of peptizing agent and a high concentration ofthe hydrosol are also essential for the further treatment, becausegenerally with an increased content of peptizing agent the gel characterof the products more and more disappears and a 'prolonged dehydration isalso of unfavorable influence. The .highly concentrated viscoushydrosols obtained according to our said processare dried under mildconditions, pref- .erably in vacuo. In order to convert them into stablegels they are finally heated to be: tween about 500 and 600 0.,preferably by degrees. By this process coarse-grained, hard gels ofglass-like appearance are obtained which are irreversible in contactwith eeing from water i water and are characterized by a high adsorbinand catalytic efliciency.

he process here described is applicable to all metal hydroxids which arecapable of forming chemical or molecular compounds with water, such asiron hydroxid, alumina,- thoria, chromium hydroxid and the like.

The process is applicable also when mixed gels consisting of severalmetal oxids are to be prepared. We have found that in this instancesalts are less suitable for use as peptizing agents than acids, amongwhich readily volatile mineral acids such as hydrochloric or nitric acidgive especially good results. We I have further found that particularlyvaluable mixed gels are obtained by starting from .equimolecularproportions of. the components.

The following examples will further illustrate how our. invention may becarried out in practice, but the invention is not limited to theseexamples.

' Ewample 1 1 kilogram of thorium nitrate is dissolved in 30 litres ofwater and precipitated as bydroxid by means of the theoreticallyrequired quantity of ammonia. The hydroxid is filtered off and washeduntil free from electrolyte and then heated to about 100 C. whilevigorously agitatin with a stirrer until a thinly liquid mass is ormed.While continuing the stirring at the same temperature so much ofcrystallized thorium nitrate is gradually added as corresponds to 29grammes of anhydrous thorium nitrate. The mass is further heated until aclearsol is obtained. Thesol is evaporated in vacuo as far as possibleand then heated while slowly raising the temperature to 500 to 600 0.Hard, glass-like lumps of a gel are obtained which is irreversibystirring at 100 while gradually adding,

oxid mixture is filtered washed and then mechanically dispersed to cubiccentimetres of double normal nitric acid until a clear sol is obtamed.The further treatment is the same as described in Example 1.

Example 3 3.7 kilograms of aluminium nitrate and 1 kilogram of ironnitrate are dissolved and both metals precipitated with ammonia ashydroxids. After being filtered oil and washed, the h droxids aretreated at about 100 C. in a much of double normal nitric acid as toobtain a clear sol. From this'sol hard ieces of a gel of glass-likecharacter are o tained by further treatment according to Example 1.

What we claim is:

1. The process of producing metal oxid gels of high adsorbing andcatalytic efliciency which comprises peptizing a freshly precipitatedmetal hydroxid by the action of an agent of acidreaction and intensiveagitation, dehydrating the resulting highly concentrated hydrosol undermild conditions and heating it slowly to between 500 and 600 C.

2. The process of producing metal oxid gels of high adsorbing andcatalytic efficiency which comprises peptizing a freshly precipitatedmetal hydroxid in the form of a concentrated suspension by treatmentwith an acid and by intensive agitation, dehydrating the resultinghighly concentrated hydrosol in vacuo and heating it slowly by degreesto between 500 and 600 C.

In testimony whereof we have hereunto set our hands.

ROBERT GRIESSBACH. JULIUS EISELE.

atting-or ball mill with so

